Another episode in the continuing series – Tiljander and Upside Down Mann.
As CA readers are aware, the “big news” of Mann et al 2008 was its claim to have got a Hockey Stick without Graybill’s bristlecone chronologies (camouflaged as a “no-dendro” reconstruction). CA readers are aware that this claim depended on their use of contaminated modern portion of the Tiljander sediments and that the original claims for a “validated” no-dendro reconstruction prior to 1500 fell apart, even though no retraction or corrigendum to the original Mann et al (PNAS 2008) has been issued.
As we learned (from an inline comment by Gavin Schmidt in July 2010), Mann et al have conceded that these claims fell apart, but did so using a “trick” (TM- climate science.) Instead of acknowledging the false assertions at the journal in which the assertions were made (PNAS), they acknowledged the failure of the no-Tiljander no-bristlecone reconstructions deep in the Supplementary Information of a different paper (Mann et al, Science 2009) – a trick for which the term “Mike’s PNAS trick” is surely appropriate (though the term “Mike’s Science trick” also merits consideration.)
The failure to retract Mann et al 2008 from PNAS has, in turn, either tricked IPCC Chapter 5 authors (or been ignored by them.) CRU’s Tim Osborn, one of the most visible Climategate correspondents, is one of the Lead Authors of Chapter 5. (Had the climate “community” given a damn about public opinion, they would have insisted that IPCC locate a Lead Author for this section who was not quite so intimately involved in Climategate. By failing to do so, they have more or less given the finger to the rest of society.)
Here’s how CRU’s Tim Osborn and his Chapter 5 coauthors assess upside-down Mann:
Mann et al. (2008) used an expanded database of proxy records and two statistical methods and found enhanced amplitude of millennial NH temperature variations, a warmer MCA than in some previous work though perhaps still cooler than the modern warm period, and that similar findings were obtained without using tree-ring data.
Thousands of blog readers are aware that the “similar findings…without tree-ring data” were obtained only by including upside-down contaminated data. It’s disquieting that IPCC coauthors are unaware of this. The failure of Mann and his coauthors to retract or correct the PNAS 2008 article lingers on.